Michael J. Baum is applying for the Renewal of an NIMH Research Scientist Award. His research concerns behavioral, neuroendocrine, and neuroanatomical aspects of sexual differentiation in a carnivore, the ferret. Working in the Department of Biology at Boston University, Dr. Baum seeks to establish general principles of reproductive behavioral and neuroendocrine development in the two sexes which apply to higher mammals. Three sets of experiments are proposed: The first will determine whether chemosensory stimuli play different roles in sexual partner selection by males and females and whether a sexually dimorphic group of galanin neurons, present in the male ferret's dorsal preoptic area/anterior hypothalamus (POA/AH), contributes to the male-typical profile of sexual partner preference. To achieve these goals, Dr. Baum will compare the effects of olfactory bulb deafferentation on sexual partner preference in gonadectomized, steroid-treated male and female ferrets. He will also determine whether intracerebroventricular infusion of galanin or of a galanin antagonist modifies the sexual partner preference of gonadectomized, steroid-treated ferrets. A second set of studies will explore sex differences in the functional neuroanatomy of the circuits which convey genital-somatosensory inputs to medio-basal hypothalamic luteinizing hormone releasing hormone (LHRH) neurons after mating. Initially, anterograde and retrograde tract tracing methods will be combined with immunocytochemistry for LHRH together with the nuclear transcription factor, Fos, to specify the neuroanatomical pathway whereby receipt of an intromission activates hypothalamic non-LHRH and LHRH neurons in estrous female ferrets. Then retrograde tract tracing will be combined with LHRH/Fos immunocytochemistry as well as excitotoxic lesions to explore the mechanism which normally prevents intromissive stimulation from activating hypothalamic non-LHRH and LHRH neurons in breeding male ferrets. A final set of experiments will compare mating- and steroid-induced changes in LHRH gene expression in medio-basal hypothalamic neurons of males and females. Dr. Baum will learn the in situ hybridization techniques needed to carry out these studies from Dr. Beverly Rubin, director of the hybridization core facility at the NIH-funded Center for Reproductive Research, Tufts Medical School. The results of the proposed studies should provide new insights into the mechanisms controlling psychosexual and neuroendocrine facets of sexual differentiation in man.